The present invention relates to a concrete filled steel tube column and method of constructing same, the concrete filled steel tube column being for use in, for example, columns and piles of building structures.
Heretofore, this kind of concrete filled steel tube column is constructed by erecting a steel tube which also serves as a formwork other than a casing and then by filling the steel tube with a concrete to form a concrete core. The steel tube and the concrete core show integral behavior when an axial compression is applied to the steel encased concrete column since they are bonded to each other. When the concrete column is subjected to an axial compression beyond a predetermined compression strength, excess strains develop in the steel tube and the concrete core, resulting in that local buckling is produced in the steel tube or in that the steel tube reaches a yield area under Mieses's yield conditions. Thus, the steel tube does not provide the concrete core with sufficient confinement, which causes the concrete core to reach a downward directed area of the stress-strain curve at a load applied considerably lower than a predetermined load. For this reason, it cannot be expected to efficiently enhance the concrete core in compression strength by the lateral confinement of the steel tube and hence a relatively large cross-sectional area must be given to the concrete filled steel tube column to provide sufficient strength to it.